Sheep oestrosis (Oestrus ovis Linne 1761, Diptera : Oestridae) in Sardinia, Italy

Oestrosis, the nasal myiasis of sheep and goats, is caused by the larvae of Oestrus ovis L. 1758 (Diptera, Oestridae) that develop from the first to t he third stage larva in the nasal cavities and frontal sinuses of affected animals. The authors report the results of an epidemiological study of oest rosis of sheep in Sardinia, Italy. Heads of 6-month to 10-year-old Sardinia n sheep (n = 566) from 124 free-ranging flocks were examined for the presen ce and location O. ovis larvae from December 1996 to November 1997. Larvae were collected, counted, and larval stages were identified. O. ovis larvae were found in 100% of examined flocks and in 91% (514/566) of examined shee p. The monthly prevalence ranged from 69% in May to 100% in July. First sta ge larvae were found in 82% (463) of all heads examined, second stage larva e in 65% (367) and third stage larvae in 10% (56). The majority of sheep ha rboured first stage larvae, with prevalences of over 80% throughout most of the study period. The prevalence of O. ovis found in this study of Sardini an sheep is the highest reported in the Mediterranean area. The high percen tage of first stage larvae found throughout the entire study period may be due to a brief period of decreased rate of larval maturation, in particular in December 1996 (96%) and January-October 1997 (94%). Third stage larvae were consistently present, often however, with extremely low prevalences co mpared to total larval burden. (C) 2001 Elsevier Science B.V. All rights re served.